• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.6
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• pp.719-724
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• 2019

This study is an extension of our previous model for a size-based fish stock assessment. In the previous model, we applied an allometric length-weight relationship (W=α·L^β) to convert lengths of fish to weights, and estimated those parameters α and β, using data about lengths and weights aggregated over years. In this study, we focused on whether consideration of temporal (e.g., year-to-year) variability in those estimates (i.e., ${\hat{\alpha}}$ and ${\hat{\beta}}$) would contributive. After calculating year-specific estimates (i.e., year-specific pairs of ${\hat{\alpha}}$ and ${\hat{\beta}}$) by applying data about lengths and weights separated by year, we evaluated the contribution of those year-specific pairs of ${\hat{\alpha}}$ and ${\hat{\beta}}$ to the performance of the size-based stock assessment model. The model with such year-to-year variability being considered (lower AIC) outperformed that with the variability being ignored (higher AIC). We illustrated this study using data on Korean chub mackerel Scomber japonicus from 2005-2017.

• Journal of Aquaculture
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• v.5 no.1
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• pp.29-67
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• 1992

Life cycle and seed production of the freshwater prawn, Macrobrachium nipponense, were studied and the results are as follows : 1. Larval development : Embryos hatched out as zoea larvae of 2.06 mm in mean body length. The larvae passed through 9 zoea stages in $15{\~}20$ days and then metamorphosed into postlarvae measuring 5.68 mm in mean body length. Each zoea stage can be identified based on the shapes of the first and second antennae, exo- and endopodites of the first and second pereiopods, telson and maxillae. 2. Environmental requirements of zoea larvae : Zoea larvae grew healthy when fed with Artemia nauplii. Metamorphosing rate was $65{\~}72{\%}$ at $26{\~}28\%$ and $7.85{\~}8.28\%_{\circ}Cl.$. The relationship between the zoeal period (Y in days) and water temperature (X in $^{\circ}C$) is expressed as Y=46.0900-0.9673X. Zoeas showed best survival in a water temperature range of $26{\~}32^{\circ}C$ (optimum temperature $28^{\circ}C$), at which the metamorphosing rate into postlarvae was $54{\~}72\%$ The zoeas survived more successfully in chlorinity range of $4.12{\~}14.08{\%_{\circ}}Cl.$, (optimum chlorinity $7.6{\~}11.6\;{\%_{\circ}}Cl.$.), at which the metamorphosing rate was $42{\~}76{\%}$. The whole zoeal stages tended to be longer in proportion as the chlorinity deviated from the optimum range and particularly toward high chlorinity. Zoeas at all stages could not tolerate in the freshwater. 3. Environmental requirements of postlarvae and juveniles : Postlarvae showed normal growth at water temperatures between $24{\~}32^{\circ}C$ (optimun temperature $26{\~}28^{\circ}$. The survival rate up to the juvenile stage was $41{\~}63{\%}$. Water temperatures below $24^{\circ}C$ and above $32^{\circ}$ resulted in lower growth, and postlarvae scarcely grew at below $17^{\circ}C$. Cannibalism tended to occur more frequently under optimum range of temperatures. The range of chlorinity for normal growth of postlarvae and juveniles was from 0.00 (freshwater) to $11.24{\%_{\circ}}Cl.$, at which the survival rate was $32{\~}35\%$. The postlarvae grew more successfully in low chlorinities, and the best growth was found at $0.00\~2.21{\%_{\circ}}Cl.$. The postlarvae and juveniles showed better growth in freshwater but did not survive in normal sea water. 4. Feeding effect of diet on zoea Ilarvae : Zoea larvae were successfully survived and metamorposed into postlarvae when fed commercial artificial plankton, rotifers, and Artemia nauplii in the aquaria. However, the zoea larvae that were fed Artemia nauplii and reared in Chlorella mixed green water showed better results. The rate of metamorphosis was $68\~{\%}75$. The larvae fed cow live powder, egg powder, and Chlorella alone did not survive. 5. Diets of postlarvae, juveniles and adults : Artemia nauplii and/or copepods were good food for postlarvae. Juveniles and adults were successfully fed fish or shellfish flesh, annelids, corn grain, pelleted feed along with viscera of domestic animals or fruits. 6. Growth of postlarvae, juveniles and adults : Under favorable conditions, postlarvae molted every five or six days and attained to the juvenile stage within two months and they reached 1.78 cm in body length and 0.17 g in body weight. The juveniles grew to 3.52 cm in body length and 1.07 g in body weight in about four months. Their sexes became determinable based on the appearance of male's rudimental processes (a secondary sex character) on the endopodites of second pereiopods of males. The males commonly reached sexual maturity in seven months after attaining the postlarvae stage and they grew to 5.65 cm in body length and 3.41 g in body weight. Whereas the females attained sexual maturity within six to seven months, when they measured 4.93 cm in body length and 2.43 g in body weight. Nine or ten months after hatching, the males grew $6.62{\~}7.14$ cm in body length and $6.68{\~}8.36$ g in body weight, while females became $5.58{\~}6.08$ cm and $4.04{\~}5.54$ g. 7. Stocking density : The maximum stocking density in aquaria for successful survival and growth was $60{\~}100$ individuals/$\ell$ for zoeas in 30-days rearing (survival rate to postlarvae, $73{\~}80{\%}$) ; $100{\~}300$ individuals/$m^2$ for postlarvae of 0.57 cm in body length (survival rate for 120 days, $78{\~}85{\%}$) ; $40{\~}60$ individuals/$m^2$ for juveniles of 2.72 cm in body length (survival rate for 120 days, $63{\~}90{\%}$) : $20{\~}40$ individuals/$m^2$ for young prawns of 5.2 cm in body length (survival rate for 120 days, $62\~90{\%}$) ; and $10\~30$ individuals/$m^2$ for adults of 6.1 cm in body length (survival rate for 60 days, $73\~100{\%}$). The stocking density of juveniles, youngs and adults could be increased up to twice by providing shelters.

• Korean Journal of Ichthyology
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• v.27 no.2
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• pp.133-141
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• 2015

Age and growth of redlip mullet, Chelon haematocheilus were determined using samples collected in Han River estuary of Korea from June, 2013 to May, 2014. Age was determined from sagital otoliths and Annul marks were formed in January once a year. In addition, spawning season was estimated in May, thus first ring was formed 8 months. The mullets were principally composed of 0 to 3 years old and the oldest was 9 years old. Relationship between standard length (SL) and total weight (TW) were $TW=0.0124SL^{3.0133}$($r^2=0.9931$). The Von Bertalanffy growth parameters estimated were $L_{\infty}$ 61.3, $W_{\infty}$ 3,230.6, K 0.29/year, $t_0$ - 0.05 year.

• Korean Journal of Environmental Biology
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• v.40 no.2
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• pp.138-147
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• 2022

Paddy fields are important habitats for maintaining the biodiversity of agricultural ecosystems. Recently, as the need for safe food and biodiversity conservation has increased, the rice cultivation methods have undergone changes. This study was conducted to investigate the fish fauna in Environmentally Friendly Paddy fields (EFP) and Conventional Paddy fields (CP), and compare the characteristics of Misgurnus anguillicaudatus and Aphyocypris chinensis populations in EFP and CP. A total of 2,703 fish were collected and classified into six families and 13 species. Our results showed that there was a difference in the proportion of fish populations in the two paddy fields, and the number of individuals in EFP was higher than in CP. The weight values of M. anguillicaudatus were higher in EFP than in CP, and the total length, body length, and weight values of A. chinensis were higher in EFP than in CP. Conditional factor(K) values also showed similar trends in EFP and CP. Our results indicate that the farming practices in paddy fields have a significant effect on the characteristics of M. anguillicaudatus and A. chinensis populations, and the results of this study can be used as basic data for securing biodiversity in future agricultural ecosystems.

• Korean Journal of Ichthyology
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• v.22 no.1
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• pp.34-40
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• 2010

The reproductive ecology of the goldeye rockfish (Sebastes thompsoni) was examined using 421 specimens collected monthly from January to December 2005 in the coastal waters of Busan, Korea. Specimens ranged in standard length (SL) from 13.8 to 31.8 cm. The gonadosomatic index (GSI) of females was highest in March and decreased until June. In males the GSI was the highest in February after that the values declined. The spawning season lasted from January to June, and the ratio of female to male did not differ significantly ($x^2$-test, p>0.05). The length at first spawning was 16.8cm SL, and the size at 50% maturity was estimated at 20.11 cm SL. All females more than 25 cm SL were sexually mature and the egg diameters were from 0.60 to 1.75 mm. Fecundity (F) ranged from 23,881 to 44,509 eggs, with a mean of 30,937 eggs. The relationship between fecundity and standard length was estimated as F=9.3762 $SL^{1.1662}$ ($R^2$=0.81). The relationship between fecundity and body weight (BW) was estimated as F=184.37 Ln (BW) - 665.09 ($R^2$=0.87).

• Korean Journal of Environment and Ecology
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• v.28 no.3
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• pp.281-286
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• 2014

This study was conducted to investigate the individual size and age of Kaloula borealis, a pair in amplexus. In June 2013, the total 23 pairs of Kaloula borealis were captured in the wetland located in Seongsan-eup and Daejeong-eup, Jeju Island. Size and age of each individual have been examined and as a result of analyzing SVL (snout-vent length), weight, length of forelimb and hindlimb of the collected 23 pairs, the females were shown to have the heavier weight and the longer SVL and hindlimb compared to males. No significant difference in the length of forelimb has been found between the female and the male. The average age of the male of the pair in amplexus was shown to be $5.17{\pm}0.26$, whereas the female was shown to be $6.22{\pm}0.28$, which indicates the higher average age in female compared to the male. The age range of Kaloula borealis was distributed from at least 3 years to 10 years at the maximum. A positive correlation was shown between age of the male and SVL; however, no significant difference was found in female. This study result expected to be utilized as an important base data in establishing the preservation and restoration strategy of endangered species, Kaloula borealis.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.5
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• pp.790-793
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• 2020

Length-weight relationships (LWR) for 27 fish species inhabit Southern sea in Korea were investigated to describe several biological characters. Total 7,399 individuals were collected by R/V Tamgu-20 using bottom trawl between 2018 to 2019 and were identified as 19 families and 27 species. Parameter b ranged from 2.414 to 3.472. Thirteen species among 27 species showed isometric growth (b=3), six species showed negative allometry (b<3) and eight species showed positive allometry (b>3). The results of this study provide useful basic biological information about 27 fishes and are highly reliable due to use of data measured directly.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.82-90
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• 2010

The ecological characteristics of the Korean Aucha perch, Coreoperca herzi, were determined in order to estimate stock of the mid-upper system of the Seomjin River. The age was determined by counting the otolith annuli. The oldest fish observed in this study was 5 years old. Relationships between body length (BL) and body weight (BW) were $BW=0.0195BL^{3.08}$ ($R^2=0.966$) (p<0.01). Relationships between the otolith radius (R) and body length (BL) were BL=3.882R+1.66 ($R^2=0.944$). The von Bertalanffy growth parameters estimated from a non-linear regression method were $L_{\infty}=19.68\;cm$, $W_{\infty}=188.64\;g$, $K=0.17\;year^{-1}$ and $t_0=-1.46$ year. Therefore, growth in length of the fish was expressed by the von Bertalanffy's growth equation as $L_t=19.68$ ($1-e^{-0.17(t+1.46)}$) ($R^2=0.997$). The annual survival rate (S) was estimated to be $0.666\;year^{-1}$. The instantaneous coefficient of natural mortality (M) of estimated from the Zhang and Megrey method was $0.346\;year^{-1}$, and instantaneous coefficient of fishing mortality (F) was calculated $0.061\;year^{-1}$. From the estimates of survival rate (S), the instantaneous coefficient of total mortality(Z) was estimated to be $0.407\;year^{-1}$.

• Korean Journal of Ichthyology
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• v.20 no.1
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• pp.21-27
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• 2008

A total sample of 215 specimens of the Iksookimia koreensis was collected monthly from June 2004 to June 2005 in the Namdae stream, Cheorwon-gun, Gangwon-do, Korea. The age of every individual sample was estimated by the number of annual rings on the scales. A significant decrease of gonadosomatic index was noted between May and June reflecting the reproduction during this period. I. koreensis exhibited a strong bias to female (female : male, 1 : 0.56). The maximum age observed was 3 years old for male & female, both. The von Bertalanffy growth curves were expressed as $L_t=126.30[1-\exp\{-0.576(t+0.940)\}]$ for females and $L_t=100.19[1-\exp\{-1.119(t+0.695)\}]$ for males.Growth curve of weight was expressed as $W_t=11.567[1-\exp\{-0.576(t+0.940)\}]^{3.199}$ for females, $W_t=5.514[1-\exp\{-1.119(t+0.695)\}]^{3.199}$ for males. On the other hand, a significant difference in the growth rate between both sexes was found(i.e. females grew faster than males).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.3 no.4
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• pp.219-227
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• 1970

The shrimp fishery for Penaeus japonicus on the Koje-Do coast commences in May and continues to October. The best catches are made twice a year, namely June and September. Modal carapace length for the female is $51\~55\;mm$ in May, $51\~60\;mm$ in June occupying about 80 percent of the total catch. There is conspicuous mode in July and $46\~50\;mm$ in August. Modal carapace length for the male is $41\~45\;mm$ in May, $46\~50\;mm$ in June, $41\~45\;mm$ in July and August. The stock of p. japonicus can be divided into two groups, namely, spring and fall groups. Among samples of p. japonicus during the period from May through August the sex ratio consisted of about 33 percent females and 67 percent males, showing wide departure from a 1:1 ratio. The relationships between carapace length ($\iota$), body length (L) and body weight (W) are expressed by the following formulae : $$L=2.9418{\iota}+2.0166$$, $$W:1.449{\iota}^{2.2858}$$ (Mayssample) $$L=2.5551{\iota}+4.2986$$, $$W=1.528{\iota}^{2.2595}$$ (June sample) $$L=2.6738{\iota}+3.4037$$, $$W=1.341{\iota}^{2.3598}$$ (July sample) The relatlonship between carapace length ($\iota$) and ovary weight (W) is shown as follows: $W=2.695\times10^{-3}\iota^{4.2973}$ for May, June and July Samples.